The present invention is concerned with a recycling process. More particularly, the present invention is concerned with an improved recycling process for unsorted waste, for example waste generated by the retail industry. The present invention is also concerned with a method of manufacturing three dimensional objects from unsorted waste, for example waste generated by the retail industry.

Current methods for the management or disposal of waste include burying the waste in the ground (landfill), incineration and recycling.

Waste generated by the retail industry includes items which have been manufactured from polymeric materials, glass, synthetic fabrics, natural fabrics (such as cotton and leather), as well as metals. The items include packaging (for example carrier bags, boxes and other containers), discarded stock (such as clothes, bags and shoes) and discarded merchandising items or fixtures and fittings from a shop (for example display boards).

Unsorted waste has been buried at landfill sites around the world for many decades. The disadvantages associated with this approach to waste disposal are numerous. One such disadvantage is the risk of soil or groundwater in the area around the landfill site becoming contaminated with rainwater that has percolated through the waste and has material from the waste dissolved or suspended in it.

Incineration is an alternative process for unsorted waste. The waste is burned and converted into ash, flue gas and heat. Gaseous and particulate pollutants must be removed from the flue gas before the flue gas is released into the environment. Some systems are set up to generate electric power from the generated heat.

Recycling is a popular alternative to burying or incinerating waste. Recycling processes generally aim to save material, minimise energy usage and reduce the pollution of soil, water or air. Waste that is to be recycled is typically sorted and cleaned prior to reprocessing into new materials and products. The sorting and cleaning of waste is either carried out manually or with the use of automated systems. Each of these sorting methods increases the cost and reduces the economic efficiency of recycling as an approach to waste processing.

There is also a desire for recycled waste to be repurposed as part of a circular system to minimise the use of raw or virgin materials and to minimise waste, pollution and carbon emissions. According to a first aspect of the invention, there is provided a method of recycling waste, wherein the method of recycling waste includes mechanically processing the waste and mixing the mechanically processed waste with a binding agent. Preferably, the waste is unsorted waste.

By unsorted waste we mean waste that includes a variety of unsorted waste items, including different products and packaging made from a range of materials including glass, plastic, metal and fibrous materials. The range of materials may include a mixture of natural and man-made, or synthetic, materials.

By removing the need to sort the waste according the material the waste items are manufactured from, the cost of the recycling process is reduced and the economic efficiency of the process is improved.

The step of mechanically processing the waste may include using more than one mechanical process, thereby using more than one machine or piece of equipment. The step of mechanically processing the waste may, for example, include using a first mechanical process and a second mechanical process, wherein the second mechanical process is different to the first mechanical process.

The first mechanical process may, for example, be a shredding process. The shredding process may be carried out using an industrial shredder or grinder. The first mechanical process may result in the formation of a granular material having a first particle size in the range of 0.5 millimetres to 20 millimetres.

The second mechanical process may, for example, be a crushing or pulverising process. The crushing or pulverising process may be carried out using a hammer mill. The second mechanical process may result in the formation of a powder having a second particle size in the range of 0.005 millimetres to 0.4 millimetres.

The step of mechanical processing the waste can advantageously be optimised to form a fine, sand like, material which can be used as an alternative to natural sand. This offers a further environmental benefit as natural sand is a non-renewable resource.

By binding agent we mean a component or agent which enables the granular and powder materials which are formed from the waste (the mechanically processed waste) to be bound or adhered together to form a solid material.

The mixture of the mechanically processed waste and the binding agent may include at least 40% binding agent. Preferably, the mixture of the mechanically processed waste and the binding agent includes at least 50 wt% binding agent and/or less than 75 wt% binding agent. The binding agent may include an organic binding agent. Alternatively, the binding agent may include an inorganic binding agent.

The binding agent may include a first component and a second component. The binding agent may include at least 65 wt% of the first component and/or less than 85 wt% of the first component.

The first component may include calcium, for example calcium carbonate.

Additionally, or alternatively, the second component may include calcium, for example calcium sulphate hemihydrate.

The mixture of the mechanically processed waste and the binding agent may be further mixed with a liquid to form a moulding material. The liquid may include water, for example waste water. The waste water may preferably be non-sewage waste water, such as surface water (i.e. collected rain water) or grey water (water that originates from non-toilet or food fixtures).

The method of recycling waste may further include adding a pigment to the moulding material. The pigment may be added to the moulding material as a solid material (for example in granule or powder form) or as a liquid.

The method of recycling waste may further include pouring the moulding material into a mould. The method may further include curing the moulding material in the mould to form a three dimensional object.

Examples according to the present invention will now be described with reference to the accompanying Figures, in which:

Figure 1 is a flow chart a method of recycling waste according to the present invention;

Figure 2a is a schematic side view of a mould for casting a three dimensional object;

Figure 2b is a schematic side view of the mould of Figure 2a into which moulding material has been poured; and

Figure 3c is a schematic side view of the mould of Figure 2b with the moulded object removed.

Referring to Figure 1, the steps 10, 12, 14, 16, 18 in a process 20 for recycling are schematically represented. In the first step 10 of the process 20, waste 22 is collected into a suitable container (not shown). The waste 22 includes a variety of unsorted waste items, including different products and packaging made from a range of materials including glass, plastic, metal and fibrous materials. The range of materials may include a mixture of natural and man-made, or synthetic, materials. At step 12, the waste 22 is broken down into granular material 24 by a shredding process. The shredding process may be carried out using any suitable machine such as an industrial shredder or grinder. The resulting granular material 24 has an average particle size in the range of 0.5 millimetres to 20 millimetres.

At step 14, the granular material 24 is crushed or pulverised into a fine powder, or sand-like, material 26. The pulverising step may be carried out using any suitable machine such as a hammer mill. The resulting powder 26 has an average particle size in the range of 0.005 millimetres to 0.4 millimetres.

At step 16, the powder 26 is mixed with a binding agent 28, for example an inorganic binding agent such as an inorganic binding agent including calcium. The inorganic binding agent including calcium may include a mixture of one or more of calcium carbonate, calcium sulphate (e.g. calcium sulphate hemihydrate), calcium oxide and calcium hydroxide. The inorganic binding agent including calcium may be provided in the form of limestone, lime, cement, plaster of Paris or gypsum. In embodiments of the invention, the resulting mixture of the powder 26 and the binding agent 28 includes 25 to 75 wt% of the binding agent.

In an exemplary embodiment of the invention, the binding agent 28 may be a mixture of two components. One or both of the two components may be an inorganic binding element, such as an inorganic binding element including calcium. The first component may, for example, be calcium carbonate. Additionally, or alternatively, the second component may be, for example, calcium sulphate hemihydrate. The binding agent 28 may include 65 wt% to 85 wt% of the first component.

Calcium sulphate hemihydrate advantageously reduces the time taken for the mixture to cure or bind together.

At step 18, the powder 26 and the binding agent 28 are combined with a liquid to form a mixture 30. In exemplary embodiments of the invention, the liquid may be water, for example waste water. By waste water we mean non-sewage waste water, such as surface water (i.e. collected rain water) or grey water (water that originates from non-toilet or food fixtures). In exemplary embodiments of the invention, the resulting moulding material 30 may include 20 vol% to 40 vol% of the liquid.

The components of the binding agent 28 react with the water to ensure that the particles of the powder 26 are bound together.

The manufacture of a three-dimensional structure using the mixture 30 will now be described with reference to Figures 2a, 2b and 2c. Referring now to Figure 2a, there is shown a mould 32. The mould 32 has a body 34 having an upper surface 36 in which a cavity 38 is formed.

As shown in Figure 2b, moulding material 30 is transferred into the cavity 38 of the mould 32. The moulding material 30 is cured at approximately 15 to 25 °C for between 10 and 30 minutes to form a moulded or cast object 40, as shown in Figure 2c.

The components of the binding agent 28 are selected to ensure that the moulded or cast object 40 can be formed within a reasonable period of time and that the finished product has the required mechanical properties for its intended application or use.

Calcium sulphate hemihydrate has, for example, been found to reduce the time taken for the moulded or cast object 40 to cure or bind. In addition, the calcium sulphate hemihydrate has been found to act as a stabiliser, thereby preventing degradation of the moulded or cast object 40.

The invention enables unsorted waste (including items manufactured from a variety of different materials) to be repurposed into other items. Examples of such repurposed, three dimensional, items include bricks, shop fittings (such as table tops) and mannequins. It will be understood that the moulded or cast object 40 could be any three dimensional shape.

Variations fall within the scope of the present invention.

A pigment or dye may be added to the process in order to ensure that objects cast from the moulding material 30 are a particular colour. The pigment or dye may, for example, be added to the process at step 16, when the powder 26 is combined with the binding agent 28, or at step 18, when the powder 26 and the binding agent 28 are mixed with the water. Alternatively, the pigment or dye may be added to the moulding material 30 prior to the casting process. The pigment may be added to the moulding material as a solid material (for example in granule or powder form) or as a liquid.

In the embodiments described, the binding agent 28 is an inorganic binding agent, such as an inorganic binding agent including calcium. In alternative embodiments of the invention, an organic binding agent, such as a polymer or a resin, may be used as the binding agent.